which data can be stored in log files i.e commited or uncommited?

Question

hi sir,

  plz expline exact which data can be stored in log files?

      i.e coomiteddata

             or 

        uncommited data

  sir iam self lerning sa sqldba plz briefly explaine which data can be stored in which files.

Regards:

Bhaskar

Answer 1

plz expline exact which data can be stored in log files?

Hello Bahskar,

Youself can't store anything directly in the log file, it's utilized by SQL Server to handle transaction data.

See MSDN The Transaction Log (SQL Server) and follow up links.

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Olaf Helper
Blog Xing

Answer 2

You can store both commited or  uncommited type of data in log files of database. But recycle of ldf depands on database recovery model.

• Full recovery model - Every commited or  uncommited data stores in log file > data commited & log backup occure > Log file become empty for reuse
• Bulk-logged recovery model - Every commited or  uncommited data stores in log file depand on bulk opearation or not > data commited & log backup occure > Log file become empty for reuse
• Simple recovery model - Every commited or  uncommited data stores in log file > data commited & checkpoint occur > Log file become empty for reuse

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Answer 3

plz briefly explaine which data can be stored in which files.

Hi Bhaskar,

SQL Server databases have three types of files:

• Primary data files
  The primary data file is the starting point of the database and points to the other files in the database. Every database has one primary data file. The recommended file name extension for primary data file is .mdf.
• Secondary data files
  Secondary data files make up all the data files, other than the primary data file. Some databases may not have any secondary data files, while others have several secondary data files. The recommended file name extension for secondary data file is .ndf.
• Log files
  Log files hold all the log information that is used to recover the database. There must be at least one log file for each database, although there can be more than one. The recommended file name extension for log files is .ldf.

For more details, please refer to this article: Files and Filegroups Architecture.

Best Regards,
Ray Chen